I know this is an old post, but i need to say the L28E is better than some of you are saying, for starters i've had a $35 pod filter dangling out the front of my engine bay for over a year now without a problem, i havent even cleaned it and its still running sweet.
As for 105kw ? are you serious?
Thats at the wheels doing 5500rpm, completely stock, with a dodgy clutch and 2 deg advanced timing (factory is 8 deg adv). Since then I've fixed the timing problems, put the pod filter on, muffler (stock pipes still), big leads / plugs and leaned out the mixture a little on the AFM. Now it chirps my 235/45/R17's into 2nd without a problem.
Also, for those interested, at dyno time it was running standard 7/11 lead replacement petrol (blue line), but on the 3rd run we added the NOS branded Octane Booster that came with some injector cleaner pack i bought, its the green line and if you look REAL close you can see its actually made a 0.02% increase in power - wow.
Go the L28E its a great motor, its (mostly) reliable and it will bolt directly into your car so there is more potential for performance because you wont need to engineer it and can spend your cash on go fast bits. If you are going to use an RB30 avoid the GM models, they overheated more due to design flaws (GM stamp on head, radiator mounting position).